JPH06139821A - Nonreducing dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a nonreducing dielectric ceramic composition not formed into a semiconductor when baked in the reducing atmosphere, capable of obtaining a large dielectric constant although the crystal grain size is small, and capable of miniaturizing a layered ceramic capacitor using it. CONSTITUTION:A nonreducing dielectric ceramic composition is mainly constituted of BaO, CaO, MgO, TiO2, ZrO2, and Nb2O5, and it is expressed by a general formula [(Ba1-xCaxMgy)O]m (Ti1-o-pZroNbp) O2+p/2, where 0<x<=0.20, 0<y<=0.05, 0<o<=0.25, 0.0005<=p<=0.023, and 1.000<=m<=1.03. The nonreducing dielectric ceramic composition contains 0.02-2.0mol. of at least one kind of oxides MnO2, Fe2O3, Cr2O3, CoO, and NiO of Mn, Fe, Cr, Co, Ni and 0.1-2.0mol. of at least one kind of SiO2 or ZnO against 100mol of the main constituent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reducing dielectric porcelain composition, and more particularly to a non-reducing dielectric porcelain composition for use in, for example, laminated ceramic capacitors.

[0002]

2. Description of the Related Art In the manufacturing process of a monolithic ceramic capacitor, first, a sheet-shaped dielectric material is prepared, the surface of which is coated with an electrode material serving as an internal electrode. As the dielectric material, for example, a material containing BaTiO ₃ as a main component is used. Sheet-shaped dielectric materials coated with this electrode material are laminated, thermocompression-bonded, and the integrated product is fired at 1250 to 1350 ° C. in a natural atmosphere,
A dielectric porcelain having internal electrodes is obtained. Then, an external electrode that is electrically connected to the internal electrode is printed on the end face of this dielectric ceramic, and a monolithic ceramic capacitor is manufactured.

Therefore, the material for the internal electrodes must satisfy the following conditions.

(A) Since the dielectric porcelain and the internal electrodes are fired at the same time, the dielectric porcelain must have a melting point higher than the firing temperature.

(B) It should not be oxidized even in an oxidizing high temperature atmosphere and should not react with the dielectric.

Noble metals such as platinum, gold, palladium or alloys thereof have been used as the electrode material satisfying such conditions.

However, while these electrode materials have excellent characteristics, they are expensive. Therefore, the ratio of the electrode material cost to the monolithic ceramic capacitor is 30 to 7
It reached 0%, which was the biggest factor in raising the manufacturing cost.

N having a high melting point other than precious metals
Although there are base metals such as i, Fe, Co, W, and Mo, these base metals are easily oxidized in a high-temperature oxidizing atmosphere and cannot serve as an electrode. Therefore, in order to use these base metals as the internal electrodes of the monolithic ceramic capacitor, it is necessary to fire them together with the dielectric ceramic in a neutral or reducing atmosphere. However, the conventional dielectric ceramic material has a drawback that it is remarkably reduced when it is fired in such a reducing atmosphere and becomes a semiconductor.

In order to overcome such drawbacks, for example, as shown in Japanese Patent Publication No. 57-42588, in a barium titanate solid solution, the barium site / titanium site ratio is set to be more than stoichiometric. The body material was devised. By using such a dielectric material, it is possible to obtain a dielectric ceramic that does not become a semiconductor even when fired in a reducing atmosphere, and it is possible to manufacture a monolithic ceramic capacitor that uses a base metal such as nickel as an internal electrode. Became.

[0010]

With the recent development of electronics, miniaturization of electronic parts has rapidly progressed, and the tendency of miniaturization of monolithic ceramic capacitors has become remarkable. As a method for miniaturizing the monolithic ceramic capacitor, it is generally known to use a material having a large dielectric constant or to thin the dielectric layer. However, a material having a large dielectric constant has a large number of crystal grains, and when the film is a thin film having a thickness of 10 μm or less, the number of crystal grains present in one layer decreases, and reliability decreases.

Therefore, the main object of the present invention is that even if it is fired in a reducing atmosphere, it does not become a semiconductor and, despite having a small crystal grain size, a large dielectric constant is obtained. It is an object of the present invention to provide a non-reducing dielectric ceramic composition capable of miniaturizing a monolithic ceramic capacitor.

[0012]

According to the present invention, the main components are composed of BaO, CaO, MgO, TiO ₂ , ZrO ₂ and Nb ₂ O ₅ , and the following general formula {(Ba _1-x Ca _x M
g _y ) O} _m (Ti _1-op Zr _o Nb _p ) O _{2 + p / 2} , where x, y, o, p and m are 0 <x ≦ 0.20,
0 <y ≦ 0.05, 0 <o ≦ 0.25, 0.0005 ≦
The relationship of p ≦ 0.023 and 1.000 ≦ m ≦ 1.03 is satisfied, and Mn, Fe, Cr, and
The oxides of Co and Ni were replaced with MnO ₂ , Fe ₂ O ₃ and Cr _{2 respectively.}
When expressed as O ₃ , CoO, and NiO, at least one kind of each oxide is contained in an amount of 0.02 to 2.0 mol, and further, 0.
1 to 2.0 mol of SiO ₂ or ZnO at least 1
It is a non-reducing dielectric ceramic composition including types.

[0013]

According to the present invention, it is possible to obtain a non-reducing dielectric ceramic composition which is not reduced even when fired in a reducing atmosphere and does not become a semiconductor. Therefore, if a porcelain multilayer capacitor is manufactured using this non-reducing dielectric porcelain composition, a base metal can be used as an electrode material.
Since it can be fired at a relatively low temperature of 250 ° C. or lower, the cost of the monolithic ceramic capacitor can be reduced.

Further, in the porcelain using this non-reducing dielectric ceramic composition, the dielectric constant is 9000 or more, and despite having such a high dielectric constant, the crystal grain is 3 μm.
Below is small. Therefore, when a multilayer ceramic capacitor is manufactured, even if the dielectric layer is thinned, the amount of crystal grains existing in the layer does not decrease unlike the conventional multilayer ceramic capacitor. Therefore, it is possible to obtain a highly reliable, small-sized, large-capacity monolithic ceramic capacitor.

The above and other objects, features and advantages of the present invention will be more apparent from the detailed description of the embodiments below.

[0016]

EXAMPLES First, as a raw material, B having a purity of 99.8% or more was used.
aCO ₃ , CaCO ₃ , MgO, TiO ₂ , ZrO ₂ ,
Nb ₂ O ₅ , MnO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , Co
O, NiO, SiO ₂ and ZnO were prepared. Using these raw materials as {(Ba _1-x Ca _x Mg _y ) O} _m (Ti _1-op Z
r _o Nb _p ) O _{2 + p / 2} represented by the composition formula, x, y, m,
Blending was carried out so that o and p were in the ratios shown in Table 1 to obtain blended raw materials. In addition, the additives (A) and (B) shown in Table 1
The number of moles of is the number of moles added to 100 moles of the main component.

[0017]

[Table 1]

The blended raw materials are wet mixed in a ball mill,
After crushing, it was dried and calcined in air at 1100 ° C. for 2 hours to obtain a calcined product. The calcined product was crushed by a dry crusher to obtain a crushed product having a particle size of 1 μm or less. Pure water and a vinyl acetate binder were added to this pulverized product, and the mixture was mixed for 16 hours with a ball mill to obtain a mixture.

After dry granulating this mixture, 2000 k
Molded with a pressure of g / cm ² , diameter 10 mm, thickness 0.5
A disc of mm was obtained. The resulting disk is 50 in air
After heating to 0 ° C. to burn the organic binder, H ₂ —N ₂ — with an oxygen partial pressure of 3 × 10 ^{−8 to} 3 × 10 ⁻¹⁰ atm was used.
In a reducing atmosphere furnace consisting of air gas, firing was performed for 2 hours at the temperature shown in Table 2 to obtain a disk-shaped porcelain.

[0020]

[Table 2]

The surface of the obtained porcelain was observed with a scanning electron microscope at a magnification of 1,500 to measure the grain size.

Then, a silver electrode was baked on the main surface of the obtained porcelain to obtain a measurement sample (capacitor). Regarding the obtained sample, the dielectric constant (ε) and the dielectric loss (tan) at room temperature
δ) and the rate of change of the capacitance (C) with respect to the temperature change were measured. The dielectric constant and the dielectric loss are measured at a temperature of 25
The measurement was performed under the conditions of ° C, 1 kHz and 1 V _rms . Regarding the rate of change of capacitance with respect to temperature change, the rate of change at −25 ° C. and 85 ° C. (Δ
C / C ₂₀ ) and the value whose change rate is the maximum as an absolute value within the range of −25 ° C. to 85 ° C. (| ΔC / C
₂₀ | _max ).

Further, the insulation resistance value was measured by applying a direct current of 500 V for 2 minutes with an insulation resistance meter. The insulation resistance was measured at 25 ° C. and 85 ° C., and the logarithm (logρ) of each volume resistivity was calculated. The results of these measurements are also shown in Table 2.

Next, the reasons for limiting each composition will be described.

{(Ba _1-x Ca _x Mg _y ) O} _m (Ti
_{In 1-op} Zr _o Nb _p ) O _{2 + p / 2} , when the calcium content x is 0 as in Sample No. 1, the sinterability of the porcelain is poor, the dielectric loss exceeds 2.0%, and the insulation It is not preferable because the resistance decreases. On the other hand, when the calcium content x exceeds 0.20 as in Sample No. 16, the sinterability deteriorates and the dielectric constant decreases, which is not preferable.

Further, when the amount y of magnesium is 0 as in sample No. 2, the insulation resistance is lowered, which is not preferable. On the other hand, as in Sample No. 17, when the amount y of magnesium exceeds 0.05, the dielectric constant decreases to less than 9000,
Insulation resistance is reduced, and the crystal grain size is larger than 3 μm, which is not preferable.

When the amount of zirconium is 0 as in Sample No. 3, the dielectric constant is less than 9000 and the rate of change in capacitance with temperature is large, which is not preferable. On the other hand, sample number 1
8, when the zirconium amount o exceeds 0.25,
The sinterability is lowered and the dielectric constant is less than 9000, which is not preferable.

As in Sample No. 4, the niobium amount p is 0.0
When it is less than 005, the dielectric constant becomes less than 9000, the crystal grain size becomes larger than 3 μm, and in the case of a laminated ceramic capacitor, the dielectric layer cannot be thinned, which is not preferable.
On the other hand, as in sample number 19, the niobium amount p is 0.023.
When it exceeds, the porcelain is reduced when it is fired in a reducing atmosphere, and it becomes a semiconductor, and the insulation resistance is significantly reduced, which is not preferable.

Like sample number 5, {(Ba _1-x Ca _x
When the molar ratio m in Mg _y ) O} _m (Ti _1-op Zr _o Nb _p ) O _{2 + p / 2} is less than 1.000, the porcelain is reduced when fired in a reducing atmosphere to become a semiconductor. Insulation resistance decreases, which is not preferable. On the other hand, sample number 20
As described above, when the molar ratio m exceeds 1.03, the sinterability is extremely deteriorated, which is not preferable.

Further, as in Sample No. 6, the main component 10
With respect to 0 mol, MnO ₂ , Fe as the additive (A)
_The amount of addition of ₂ O ₃ , Cr ₂ O ₃ , CoO, NiO is 0.0
When the amount is less than 2 mol, the insulation resistance at 85 ° C. or higher becomes small, and the reliability of long-term use at high temperature decreases, which is not preferable. On the other hand, as in Sample No. 21, when the additive amount of these additives (A) exceeds 2.0 mol with respect to 100 mol of the main component, the dielectric loss increases to more than 2.0%, and at the same time, The insulation resistance also deteriorates, which is not preferable.

In addition, as in Sample No. 7, the main component 100
SiO ₂ or Z as an additive (B), based on mol
If the amount of nO added is less than 0.1 mol, the sinterability will be poor and the dielectric loss will exceed 2.0%, which is not preferable. on the other hand,
As in Sample No. 22, S was added to 100 mol of the main component.
When the added amount of iO ₂ or ZnO exceeds 2.0 mol,
The dielectric constant decreases to less than 9000, the insulation resistance deteriorates, and the crystal grain size becomes larger than 3 μm, which is not preferable.

On the other hand, when the non-reducing dielectric ceramic composition of the present invention is used, the dielectric constant is as high as 9000 or more,
To obtain a dielectric porcelain that has a dielectric loss of 2.0% or less and a rate of change of capacitance with respect to temperature that satisfies E characteristic standard or F characteristic standard defined in JIS standard in the range of -25 ° C to 85 ° C. You can Furthermore, in this dielectric porcelain, 2
The insulation resistance at 5 ° C. and 85 ° C. shows a high value of 12 or more when expressed by the logarithm of volume resistivity. The non-reducing dielectric ceramic composition of the present invention also has a firing temperature of 1250 ° C.
It can be sintered at a relatively low temperature as
It is as small as μm or less.

In the examples, the starting material is BaC.
O ₃ , CaCO ₃ , MgO, TiO ₂ , ZrO ₂ , Nb
An oxide powder such as ₂ O ₅ may be used, or a powder obtained by an alkoxide method, a coprecipitation method, a hydrothermal synthesis method, or the like may be used. By using these powders, the characteristics shown in the examples can be improved.

Claims (1)

[Claims] 1. A main component of which is BaO, CaO, MgO,
It is composed of TiO ₂ , ZrO ₂ and Nb ₂ O ₅ , and is represented by the following general formula: {(Ba _1-x Ca _x Mgy _y ) O} _m (Ti _1-op Zr _o Nb _p ) O _{2 + p / 2} , X, y, o, p and m are 0 <x ≦ 0.20 0 <y ≦ 0.05 0 <o ≦ 0.25 0.0005 ≦ p ≦ 0.023 1.000 ≦ m ≦ 1. Satisfying the relation of 03, and for 100 moles of the main component, M
The oxides of n, Fe, Cr, Co, and Ni are mixed with MnO ₂ , F.
e ₂ O ₃ , Cr ₂ O ₃ , CoO, NiO,
0.02 to 2.0 mol of at least one kind of each oxide, and 0.1 to 2.0 mol of SiO ₂ or Zn.
A non-reducing dielectric ceramic composition containing at least one O.